Field
The described technology generally relates to an image signal modifying device and an image signal modifying method.
Description of the Related Technology
Liquid crystal displays generally include two display panels on which field generating electrodes are formed and a liquid crystal layer interposed therebetween. Typically, liquid crystal displays operate by applying a voltage to the field generating electrodes to generate an electric field in the liquid crystal layer in order to adjust the configuration of liquid crystal molecules and control the polarization of the incident light in order to display images.
Liquid crystal displays generally include pixels having a switching element such as a thin film transistor (TFT) and a display panel which is controlled by display signal lines such as gate lines and data lines. The thin film transistor serves as a switching element which either transmits a data voltage from the data line to the pixel or blocks the data voltage in accordance with a gate signal received from the gate line.
A liquid crystal capacitor generally includes a pixel electrode and a common electrode and a liquid crystal layer disposed between the two electrodes functions as a dielectric material. A data voltage is applied to the pixel electrode and a common voltage is applied to the common electrode to apply a charging voltage (also referred to as a pixel voltage) across the liquid crystal capacitor. The arrangement of the liquid crystal molecules in the liquid crystal layer is based on the magnitude of the pixel voltage and determines the polarization of light passing through a liquid crystal layer. The change in the polarization affects a change in the transmittance of light through a polarizer attached to the liquid crystal display and thus the luminance of the pixels may be controlled to reflect the gray level of an image signal.
However, the response speed of the liquid crystal molecules is relatively slow, since it takes time to reach a desired pixel voltage in the liquid crystal capacitor, it will also take time to reach the desired luminance. Therefore, when the difference between the target voltage and the previous voltage applied to the liquid crystal capacitor is large, the voltage applied to the liquid crystal capacitor may not reach the target voltage while the switching element is turned on.
One method to improve the response speed of the liquid crystal without changing its physical properties is a dynamic capacitance compensation (DCC, hereinafter referred to as DCC) method. The DCC method uses the fact that when the voltage at both ends of the liquid crystal capacitor is increased, the charging speed is increased. Therefore, the data voltage applied to the pixel (the difference between the data voltage and the common voltage, for convenience, the common voltage is assumed to be zero) is set to be higher than the target voltage, shortening the time required for the voltage in the liquid crystal capacitor to reach the target voltage.
Typically, DCC processing is performed on the image signal after performing adaptive color correction (ACC, hereinafter abbreviated as ACC). However, when a pixel is overdriven from a low gray level to a high gray level, the ACC lookup table (LUT, hereinafter referred to as LUT) is changed during the ACC processing. In this case, if a predetermined DCC LUT is used, it is difficult to precisely control the desired gray level.
Accordingly, if the ACC LUT is changed, there is a need for a device and a method which modifies the data of the DCC LUT in accordance with the change.
The above information disclosed in this Background section is only intended to facilitate understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.